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Biology > Ecosystems > Flashcards

Ecosystems Flashcards

1
Q

What is an ecosystem?

A

A set of interacting, interdependent biotic and abiotic components

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2
Q

What 2 types of factors can affect an ecosystem?

A

1- Biotic

2- Abiotic

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3
Q

What is a biotic factor?

A

A living factor

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4
Q

What is an abiotic factor?

A

A non-living factor

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5
Q

Name 5 abiotic factors

A 
1- Light
2- Temperature
3- Water availability
4- Oxygen availability
5- Edaphic soil factors
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6
Q

Name 3 biotic factors

A

Competition for:
1- Food
2- Space
3- Breeding partners

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7
Q

Explain how light is an abiotic factor

A

Photosynthesis = success of plant species

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8
Q

Explain how temperature is an abiotic factor

A
  • Enzymes = faster/slower metabolic reactions

- Migration + hibernation

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9
Q

Explain how water availability is an abiotic factor

A

Lack of water = water stress = death

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10
Q

Explain how oxygen availability is an abiotic factor

A

Aerobic respiration

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11
Q

Explain how soil factors are an abiotic factor

A

Different soil types have different sized particles which affects the organisms that can live there

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12
Q

What is biomass?

A

The mass of living material present in a particular place or in particular organisms

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13
Q

What is the easiest way of measuring biomass?

A
  • Calculate dry mass
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14
Q

How do you calculate dry mass?

A

Discount water content by:

  • Killing organism
  • Place in oven at 80°C
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15
Q

Why might dry mass not be representative?

A

Only a small sample is taken to minimise destruction of organisms

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16
Q

What are the units of biomass?

A
  • Land = g m -2

- Water = g k -3

17
Q

What is the energy available at each trophic level measured in?

A

kJ m-2 yr-1

18
Q

What is ecological efficiency?

A

The efficiency with which biomass of energy is transferred from one trophic level to the next

19
Q

Why do producers only convert 1-3% of sunlight into biomass?

A
  • Approximately 90% is reflected
  • Other factors may limit PHS
  • Some energy is lost for PHS reactions
20
Q

What is gross production?

A

The total solar energy that plants convert to organic matter

21
Q

How do you calculate net production?

A

Gross production - respiratory losses

22
Q

Why do consumers convert a maximum of 10% biomass from food to their own organic tissue?

A
  • Not all of the biomass is eaten
  • Some energy is transferred as heat
  • Some parts of an organism are indigestible
  • Some energy is lost in excretory materials
23
Q

How do you calculate ecological efficiency?

A

Energy after transfer/Energy before transfer x 100

24
Q

What can humans do to maximise ecological efficiency?

A
  • Remove predators
  • Remove competition
  • Provide food
  • Provide optimum abiotic conditions
25
Q

Describe the nitrogen cycle

A
  • Nitrogen is fixed into ammonia by Rhizobium (roots) & Azotobacter (soil)
  • Also by Haber process & lightning
  • Ammonia undergoes nitrification into nitrites, by Nitrosomonas
  • Nitrites undergo nitrification into nitrates, by Nitrobacter
  • Nitrates undergo denitrification into nitrogen gas
  • Or nitrates are taken up by plants & then to animals so plant & animal protein undergoes ammonification by decomposers into ammonia
26
Q

Describe the carbon cycle

A
  • CO2 photosynthesised into plant material
  • Carbon is transferred to animals via feeding
  • CO2 is returned to atmosphere via respiration
  • When animals/plant die, the carbon is released by decomposition back to atmosphere
  • If decomposition is prevented, carbon forms fossil fuels which, when combusted, release CO2 into atmosphere
27
Q

What is primary succession?

A

Succession that occurs on newly formed land with no organic material

28
Q

Describe the first stage of primary succession

A

Pioneer community

- Pioneer species colonises inhospitable land

29
Q

Describe the second stage of primary succession

A

Intermediate community

  • Weathering of bare rock produces basis of a soil
  • Pioneer species decompose & release humus
  • Soil can now support secondary colonisers
  • Secondary colonisers decompose & release organic material so the soil can now support tertiary colonisers etc
30
Q

What are 2 adaptations of the pioneer species?

A
  • Ability to photosynthesise

- Tolerant to extreme environments

31
Q

Describe the third stage of primary succession

A

Climax community

  • Optimum conditions
  • Environment rarely changes
  • 1 or 2 species become dominant
32
Q

What is plagioclimax?

A

The final stage of succession, when humans interrupt it

Biology (19 decks)

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